DeHavilland Canada posted on LinkedIn an image of a part needing to be shipped to repair the water bomber wing. Looks like a leading edge rib, difficult to machine on-site. Awesome it was in stock.
I’ve done urgent customer support for repairs and it’s so damn satisfying to hit that moment where parts and engineering approvals are sorted, let the techs have at it and let’s GOOOOOOO!
Making me smile tonight.
Send the bill to that drone operator though…
Surely a roll of speed tape would do the trick…
Ha!
Because I’m a nerd:
Not my discipline, but if you could make the right shape and cover the hole stiffly enough, it hypothetically could be good enough to get a ferry permit to a maintenance facility (assuming the plane was evaluated to not be able to fly as-is, for a small enough hole, and couldn’t be fixed where it is). Might be some performance penalties (assume degraded performance and use modified speeds and whatnot for dispatch, add inspections between flights if the trip is multiple legs). Speed tape is magic.
DeHavilland was clearly in the loop on this, meaning their structures, loads, performance etc experts were involved in designing and approving the repair. They’ll get the plane operational and, if necessary, follow up with the long-term damage analysis and any limitations they impose (more frequent maintenance inspections), if any.
Freaking love this stuff.
Is there any process for patching beyond just the tape? Say, take some aluminum sheet, rivet it in place loosely, and then secure it with speed tape? Might make some larger or more awkward holes a bit easier to cover. As you say, I’m imagining some performance penalties, but maybe good enough to keep the plane in action for the time being.
That’s kind of it, really. Without considering underlying structure, a hole in the skin is generally patched with a doubler. The doubler would be large enough to cover the hole and perhaps have 2 rows of rivets all around. If a static stress analysis results in this being strong enough, then off you go. Speed tape might be used to cover fasteners for aerodynamic smoothness, but realistically it isn’t actually structural at all.
The repair as done will be analyzed for longer term damage resistance, and either approved as-is (it’s equal to the original skin in strength and safety; not likely) or with limitations (probable; strong and safe provided inspections for cracks are done more frequently) or modified for something else if inadequate, likely also requiring limitations.
I’ve supported such work and designs and I know the process well, but the actual math and decisions based on that is well beyond my scope of knowledge at this point.
I should say you’d never have a permanent repair involving speed tape. It would be used to cover steps and gaps, a blown out rivet (lightning strike), or unavailability of sealant until the plane is moved. It’s a temporary thing, but totally fine with defined limits usually established in the Standard Repair Manual that operators have access to.
Q: once the landing gear is retracted, do the wheels get “braking action” (i assume)? … At what stage?
A few days late, I checked the Wiki article on wheel-well stowaways. It notes a 76% fatality rate - which means almost 1 in 4 survive.
Frostbite is common, but many cases of surviving altitudes well over 30,000’ are documented. I found this one (Aug 2000 flight from Tahiti) interesting:
Survived at 38,000 feet (12,000 m). Discovered during a refueling stopover in Los Angeles, where his body temperature had dropped to 26 °C (79 °F), well below levels usually considered lethal. Maruhi later told that the main motive behind his travel to France was to “shake hands” with Zinedine Zidane.
& roughly 20% in that list fell. A lot of airports have approaches over water; I wonder how many more fell out & became fish food never to be discovered.
In general, once the retraction cycle is triggered, the main wheels are braked to a stop before the gear legs start moving toward retraction. That prevents lots of gyro forces. The wheel brakes are powerful enough to stop the wheels in just a couple of turns when they don’t also have to try to slow the mass of the airplane. So it happens quick.
Nosewheels generally do not have brakes. Instead, when the nosegear is fully stowed in the well, the tire(s) press against an abradable bumper in the ceiling of the well and that friction drags the wheels to a stop in a 3-5 seconds. And sprays powdered / granulated hot rubber all over the interior of the nosewheel well; it’s a mess in there.
Since in most narrowbody jets the nosegear is generally beneath the cockpit, the mechanical sounds of the nose gear retraction and bumper braking is real obvious. Once the abradable part of the bumper is worn down enough, the nosewheel isn’t properly braked and take 15-20 seconds to spin down. Which long noise slowly lowering in pitch is your cue to notify maintenance to change the abradable bumper.
I hadn’t really thought about the gyroscopic forces. My dad (also a pilot) had a tractor with a belt-driven wood chipper on a three-point hitch. The belts had a tendency to slip, so my dad toyed with the idea of attaching a large flywheel to it. That got me wondering about what would happen if someone was driving the tractor while the flywheel was spinning, and the driver raised or lowered the hitch. You might be able to steer the tractor with the precession of the flywheel.
There was one airliner I know of where the nose gear retracted sideways. I wonder if that caused a noticeable gyroscopic force on the plane.
Something to consider on a quick-turn are hot wheels and brakes. They would make for a large space heater in a small space.
And a couple of cans of Old Milwaukee… I’m thinking the problem with repair is 2 part:
Consider the possibility that the drone was from an agency involved in the fire fighting effort.
Hi-lites or blinds could work, though could increase the inspection frequency (I have no specific knowledge for this case). It’s possible to certify alternates to solid rivets when there’s no space to buck; was a regular occurrence at my old job. Totally routine and in most cases an operator will accept an additional maintenance interval over scrapping their plane any day, if one is necessary due to the replacement. In many cases these substitutions are negligible and have no further consequences.
DeHavilland were clearly involved. They are the Type Certificate holder, and have a DAO with delegates who can approve changes and repairs to the aircraft design. The service request would have been handled as a priority by the in-service engineering team and approval done quickly. These specialists are good at what they do. Approval procedures for damage of this type is downright routine; only the particulars change.
I’m fairly sure I’ve read that there was a restriction on operations in the area, prohibiting anything not coordinated by the firefighting team. My comment is in that context. There doesn’t seem to be indication that drones were legally operating in that area, but I may have misunderstood.
I’m speculating they are using a doubler at all. It’s just as possible they are just installing new parts after performing detailed inspections and NDT on the affected area. If there’s nothing further than that hole in the skin, replacing the part with another is already a certified design, no additional approvals required.
I have no doubt of this. But if there are multiple agencies involved then stuff happens in the fog of war.
Sideways retracting nosegear are fun. The Hawker-Siddeley Trident is the first one that comes to mind; do you know of others?
The F-16 has a variant of that weirdness: the gear leg retracts forward like most do, but during the process the wheel rotates 90 degrees to lie flat with the axle vertical, not the wheel. There’s not enough depth in/under that chin scoop to have it oriented the usual nosegear way with the wheel(s) vertical and the axle(s) horizontal.
However the gear retracts on any airplane, the gyro forces would not be material on the overall airplane. But they sure would be material to the design of the gear leg and attachment points and actuating arms and such. All that linkage will be suffering a powerful twisting force while moving. On mains which already have brakes, easier to avoid all that with one valve that clamps the brakes on.
For the much smaller (but faster spinning) nosegear, gyro doesn’t occur on a straight retraction, be that forward or aft. And for a sideways one, or one with an F-16-style twist, more beef in the linkages & structure is probably lighter than adding even a wimpy brake and the control plumbing to a nosegear. Which plumbing would also have to deal with the nosewheel turning through almost 180 degrees of range.
The original B-727-100 was designed as a low-capacity short field airplane. Back in those days a LOT of airports were still sized for DC-4s & DC-6s which didn’t need much runway. A nosewheel brake was an optional extra to improve stopping capability. Most carriers who bought that option quickly removed it. Little real world benefit, just ballast to drag around, plus the maintenance burden of keeping it / them functional.
thx, quality info (as always)
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in my (childish) mind, I kind of auto-completed your phrase while reading it:
… it is the job of the co-pilots booty to …
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add on Q:
does that mean that the nose gear does not have wheel brakes at all? … is this “typical” for commercial jets (and by extension, assuming also for smaller-than-commercial planes)?
Nah, still worthy of fines and other punishments.
Drone operators have a responsibility to respect airspace restrictions but also to see and avoid other aircraft. A larger plane cannot be expected to spot and change it’s course in response to a drone which is too small to see (and most don’t broadcast their presence or identity).
Given the nature of operations in the area, I find it unlikely that operations beyond visual lines of sight have been authorized to anyone anywhere near that airspace right now. Which means any drone operations - even supporting - would have to maintain visual contact with their drone. I still hold them 100% responsible for this event as they would have watched their pilot fly this thing into a damn aircraft.
Besides, we know from media releases that this was a civilian drone. It was not authorized. It was not supporting operations. Throw the book at them.